No More Guesswork Mercedes-Benz sensor tells when to change oil

The new Mercedes-Benz 3.2L V-6 can do many things very well. Among them: taking the M-Class sport/utility vehicle (SUV) up steep and rocky inclines and speeding the new CLK coupe effortlessly along the autobahn.It can also tell a driver when it's time for an oil change.The three-valve per cylinder V-6 engine, which also appears on the midsize C280 sedan, is equipped with a special dielectric sensor

The new Mercedes-Benz 3.2L V-6 can do many things very well. Among them: taking the M-Class sport/utility vehicle (SUV) up steep and rocky inclines and speeding the new CLK coupe effortlessly along the autobahn.

It can also tell a driver when it's time for an oil change.

The three-valve per cylinder V-6 engine, which also appears on the midsize C280 sedan, is equipped with a special dielectric sensor in the oil pan that measures the amount and type of contaminants in the oil, as well as how the vehicle is being driven.

When an oil change is necessary, the engine computer alerts the driver by flashing an image of a wrench in the bottom center of the dashboard. To the right is a message encouraging an oil change.

The Flexible Service System, which is standard equipment on the new V-6, was developed by Mercedes-Benz and Shell Oil Co.'s Deutsche Shell of Hamburg, Germany.

Similar systems have appeared on other vehicles, but none has used a sensor precisely monitoring oil quality, says Fred Heiler, spokesman for Mercedes-Benz of North America Inc. The other systems have computed how quickly an oil change is needed based mainly on a person's driving style. An aggressive driver, for instance, would be notified sooner than a casual driver that an oil change is necessary.

"But still, it's just an educated guess," Mr. Heiler says. "When you introduce a sensor immersed in the oil pan, and an electronic signal changes based on how much dirt is in the oil, then you have a system with open eyes, so to speak.

"Ours is the only one that incorporates an actual sensor, so you really do have a feedback system."

Mercedes-Benz claims the Flexible Service System can safely extend maintenance intervals up to 20,000 miles (32,000 km) if the vehicle is driven primarily on the open road at light throttle. With heavy stop-and-go driving, the system may require maintenance every 10,000 miles (16,000 km).

The company says the engine, even without the oil sensor, is designed to go about twice as long as most engines between oil changes, thanks in part to advanced combustion design and twin spark plugs.

Mr. Heiler says he expects the system to appear on future Mercedes-Benz engines.